A Phenomenological Engine Model for Direct Injection of Liquid Fuels, Spray Penetration, Vaporization, Ignition Delay, and Combustion

A phenomenological engine model has been developed to study direct injection of liquid fuels in diesel and gasoline engines. Sub-models were obtained from the literature wherever possible and include those for initial drop size, droplet vaporization, and spray penetration. The progress of the injected spray, including both liquid and vapor, is visualized relative to the combustion chamber bowl boundaries and gives valuable insight on where the spray tip intersects the piston bowl surface, and whether it is in a liquid or gaseous state. The one-dimensional spray penetration used in the model is oblivious to surfaces (thus no spray-wall interactions), air motion, turbulence, and mixing with air, but is properly influenced by gas temperature and density. An ignition delay sub model, based on the sum of droplet vaporization time and reaction time, has been calibrated to experiments run at Sandia National Laboratories, and provides good results over a wide range of applications, including those for very late injection timings as used in low soot combustion (LSC), and those of very early injection where pre-mixed compression ignition (PCI or HCCI) combustion is desired.